Warming, western wildfires linked by new interactive map

Boulder NCAR expert, however, cautions against broad interpretations of data

By Charlie Brennan Camera Staff Writer

Posted:
07/11/2013 09:17:15 PM MDT

Hot, hot, hot

The mercury officially topped out at 98 degrees in Boulder on Thursday -- and crept up to 99 at Boulder Municipal Airport.

But that was well shy of the 104-degree record for July 11.

Friday's high is expected to hit 94, according to the National Weather Service. Forecasts call for a 30 percent chance of showers, mainly after 3 p.m.

There also is a chance of showers Saturday afternoon, when the high is expected to be near 90. Sunday also should see temperatures top out around 90, with mostly cloudy conditions and a 30 percent chance of showers and thunderstorms.

It's not as dramatic as tearful services for 19 Arizona firefighters or aerial footage of hundreds of incinerated Colorado Springs-area homes in the most destructive blaze in state history. But the fiery face of the new American west can now also be glimpsed through a new interactive online tool.

Climate Central, based in Princeton, N.J., on Thursday introduced a Web-based map that highlights the correlation over the past 42 years between increased wildfires in western states and rising spring temperatures and declining snowpack.

"I think what seems most important to see in the data is that it's completely true, that years with higher temperatures in spring and summer and lower snowpack tend to be the years with the most fires," said Alyson Kenward, a senior scientist with Climate Central.

Based in Oakland, Calif., Kenward was speaking from the embrace of the foggy cool as she drove across the Bay Bridge on Thursday. Boulder, meanwhile, was sweltering at 98 degrees. Just north of Boulder County, fire crews were battling two small blazes linked to a Tuesday lightning strike.

"It doesn't mean that every year with lower snowpack or higher temperatures will be a higher fire year, but there is definitely a trend there, that when we see higher temperatures and lower snowpack, the risk of it being a big fire year is there."

'This is a tool'

Colorado is one of 11 western states whose data is incorporated into the interactive map, utilizing fire and springtime temperature data dating back to 1970, and SNOTEL snowpack data from the Natural Resources Conservation Service going back to 1980.

With the map -- which you can see at dailycamera.com -- people can roll over individual states, and review year-by-year data that reflects the number of fires on U.S. Forest Service land of 1,000 acres or more, juxtaposed with each state's average temperature for March, April and May, and its average snowpack for April 1 of that same year.

The map shows, for example, that in 2012, the hottest spring and summer on record for Colorado, when Colorado's average springtime temperature was 49 degrees, the state recorded nine such fires. That's more than any other year in the study period except for the devastating fire year of 2002, when there were 14, including the Hayman Fire.

"This is a tool, it's not a forecast," Kenward said. "However, when we see that years with hotter temperatures and less snowpack tend to have bigger fires, it looks like a risk factor for bigger fires.

"Other research has shown we can expect higher temperatures going forward in the west, and we're also seeing that, consistently, spring snowpack is decreasing across the west. It's a hint of what we can expect" in future fire seasons.

Josh Eddy, of Boulder Roofing, adds caulking to a newly finished roof on a 98-degree day Thursday in Boulder. A new interactive online tool from Climate Central highlights the links between increased wildfires in western states and rising spring temperatures and declining snowpack. (Mark Leffingwell / Daily Camera)

'Much more complicated'

But Janice Coen, a project scientist at Boulder's National Center for Atmospheric Research who studies the effects of weather on wildfire behavior, cautioned against drawing too much from the broad outlines of the historical record offered by Climate Central's mapping tool.

In the study of wildfires, Coen said, it is as if some are focusing only on the trunk of an elephant, while others are examining elephants' toenails, while all are proposing to make broad statements about the whole animal.

"The worst part of this is, if you try to look at one metric, like drought, it could have the opposite effect in different ecosystems," Coen said.

"In certain places, for example, in an alpine forest, drought in the past year or two contributes to bigger fires. However, in grasslands, sustained drought does not lead to bigger fires. In fact, increased rain in the past year would lead to bigger fires, because it causes a lot of grass to grow and makes it more amenable to fires this year."

She pointed out that with Colorado's four most destructive fires since 2010 (in total homes burned) having occurred during years marked by drought, each of those blazes was exacerbated by coinciding "anomalous" weather events such as downslope winds.

Referring to the Climate Center maps, Coen said, "These big-picture looks are one perspective -- and one part of the problem. To anticipate what is going to happen, at any particular location, it's much more complicated."

The Natural Resources Conservation Service snow survey showed the state's snowpack on May 1 of this year at 83 percent of median, a 366 percent improvement over the levels reported at the same date in 2012. Nevertheless, more than 500 homes were destroyed just last month in the Black Forest Fire near Colorado Springs.

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